1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device having lead terminals bent in a J-shape and a method of manufacturing the semiconductor device.
2. Description of the Related Art
Conventionally, semiconductor devices such as an LSI (Large Scale Integrated Circuit) and a transistor are utilized in various electronic apparatus.
In such a semiconductor device as just mentioned, a pellet of a semiconductor circuit is encapsulated in a resin member, and a large number of lead terminals each formed from an elongated conductive plate are provided on the opposite sides of the resin member. Since the lead terminals are connected to connection pads of the pellet in the inside of the resin member, if the semiconductor device is mounted on a circuit board and the lead terminals are connected to signal lines, then various signals can be inputted to and outputted from the pellet.
While such semiconductor devices are utilized to various applications, for example, for a semiconductor device for use with a portable telephone set, it is required to minimize the mounting area. Thus, a semiconductor device wherein outer portions of lead terminals extending outwardly from side faces of a resin member are bent in a J-shape and the free ends of the lead terminals are positioned on a lower face of the resin member to reduce the mounting area has been put into practical use.
Such semiconductor devices are disclosed, for example, in Japanese Patent Laid-open No. 221242/95, Japanese Patent Laid-open No. 263607/95, and Japanese Patent Laid-open NO. 88296/96.
In a semiconductor device wherein lead terminals are bent in a J-shape and the free ends thereof are positioned on a lower face of a resin member as described above, since also the overall occupation area is decreased and the lead terminals are connected to a circuit board at positions of the lower face of the resin member, the mounting area can be reduced.
However, with such a semiconductor device as described above, since the free ends of the lead terminals are positioned on the lower face of the resin member, if a radiating plate made of a conductive island is exposed to the lower face of the resin member, then the radiating plate and the lead terminals are short-circuited to each other.
Therefore, a semiconductor device wherein the lead terminals are bent in a J-shape as described above is so structured that the radiating plate is not exposed to the lower face of the resin member, and consequently, it does not exhibit a good heat radiating property of the pellet. However, in a semiconductor device utilized for transmission of radio waves in a portable telephone set, the pellet generates a large amount of heat because it consumes a large amount of power, and therefore, it is required to radiate the heat efficiently.
In this connection, in the semiconductor device disclosed in Japanese Patent Laid-open No. 221242/95, the radiating plate is exposed to the lower face of the resin member while an insulating film is applied to the lower face of the radiating plate to prevent short-circuiting with the lead terminals. However, since this structure does not allow connection of the radiating plate to a grounding line of the circuit board, a good heat radiating property cannot be anticipated.